src: remove unused isolate member

PR-URL: https://github.com/nodejs/node/pull/7334
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Trevor Norris <trev.norris@gmail.com>

src/env-inl.h

@@ -49,8 +49,7 @@ inline IsolateData::IsolateData(v8::Isolate* isolate, uv_loop_t* event_loop,
             sizeof(StringValue) - 1).ToLocalChecked()),
     PER_ISOLATE_STRING_PROPERTIES(V)
 #undef V
-    isolate_(isolate), event_loop_(event_loop),
-    zero_fill_field_(zero_fill_field) {}
+    event_loop_(event_loop), zero_fill_field_(zero_fill_field) {}
 
 inline uv_loop_t* IsolateData::event_loop() const {
   return event_loop_;

src/env.h

@@ -330,7 +330,6 @@ class IsolateData {
 #undef VS
 #undef VP
 
-  v8::Isolate* const isolate_;
   uv_loop_t* const event_loop_;
   uint32_t* const zero_fill_field_;